/**
 * 一将下面异步代码使用 Promise 的方式改进
 * setTimeout(function () {
  var a = 'hello'
  setTimeout(function () {
    var b = 'lagou'
    setTimeout(function () {
      var c = 'I v U'
      console.log(a + b + c)
    }, 10)
  }, 10)
}, 10)
 */

new Promise((resolve, reject) => {
    let a = 'hello'
    resolve(a)
}).then(value => {
    let b = 'lagou'
    return value + b
}, error => {}).then(value => {
    let c = 'I v U'
    console.log(value + c)
}, error => {})